Electron tube for the optical indication of an electrical magnitude



ELECTRON 1111311: 'FOR THE OPTICAL INDICATION oct. 11, 1960 G H RALMA m1 2,956,194

OF. AN ELECTRICAL MAGNITUDE Filed Oct. 3. 1958 Unite States Patent Otice Patented Oct. 11, 1960 ELECTRON TUBE FOR THE GPTICAL INDICA- TION F AN ELECTRICAL MAGNITUDE Gerrit Hendrik Petrus Alma, Willem Keeman, Carel Peter Klopping, and Dirk Cornelis Kranen, ail of Eindhoven, Netherlands, assignors to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware Filed Oct. 3, 1958, Ser. No. 765,194

Claims priority, application Netherlands Oct. 4, 1957 1 claim. (ci. 313-92) The invention relates to electron tubes for the optical indication of the occurrence of an electrical magnitude such as a load, current or voltage, more particularly on a tube which may be operated at voltages lower than 100 volts and which is suitable for use in computers and counters and the like, possibly in co-operation withtransistors.

In such devices, which usually operate by the binary system, in most cases electric discharge tube indicators are used to indicate the 0- or the l-condition.

However, in transistor circuits, the voltages applied are usually too low to obtain satisfactory indication, so that it was necessary to utilize separate, higher supply voltages for these indicators.

It has been found that a distinct and reliable indication can be obtained at supply voltages below 100 volts by means of an electron tube containing a cathode, one or more grids and an anode covered with luminescent material if, according to the invention, the anode comprises a grid, the wires of which are covered with luminescent material at least for part of the surface remote from the cathode. The grid which serves as an anode is preferably arranged wholly at one side of the cathode, it -being possible for a reector electrode to be arranged at the opposite side of the cathode. termined embodiment, the wires of the anode are located in one plane. The pitch of the wires is preferably chosen to be comparatively high with respect to that of the control grid. On the one hand, the wires are required to be spaced to an extent such that electrons in suicient quantity can pass between them and, on the other hand, it is desirable for lthem to be spaced so closely that, as seen from some distance, the luminous parts of the wires seem to produce a luminous column along the longitudinal axis of the tube.

In order that the invention may be readily carried into effect, several embodiments will now be described in detail, by way of example, with reference to Ithe accompanying drawing.

In Fig. 1, reference numeral 1 indicates the bulb of a high-vacuum tube containing a lamentary cathode 2, which is surrounded by a control grid 3. A reflector elec- In one detrode 4 is arranged at one side of the cathode 2, an anode 5 arranged at the opposite side of cathode 2 comprising an elliptic grid of high pitch, of which at least the parts of the wires most adjacent the cathode are covered, on the side opposite the cathode, with luminescent material 6, such as willemite. As a rule, luminescent material is sprayed onto the whole grid. y

It has been found that electrons can penetrate from the cathode into the space enclosed by the anode 5, but substantially return as a result of space charge in this space and arrive at the luminescent surface of the parts of the Wires most adjacent the cathode. Luminescent points are then produced on the various wires, which provides a clear indication. If the control grid 3 becomes sutilciently negative, the luminous points disappear. The tube may thus provide an indication as to whether, for example, a circuit connected to the control electrode 3 conveys current or a given point has a positive or negative potential with respect to the cathode 2. The electrode 4 is connected to a low potential, for example to the negative terminal of cathode 2.

It appears that clear luminescence already occurs at an anode voltage of from 25 to 50 volts, which voltage is usually already available in computers. Furthermore, the anode current is found to be completely suppressed at a negative voltage of a few volts on control grid .3, so that this electrode may be connected, if desired, to the co1- lector of a transistor.

In the embodiment shown in Fig. 2, the anode has the shape of a half-grid 7, which may be obtained by pressing the wires of a wound grid into one plane. In Fig. 3, the anode is constituted by a at grid 8.

Fig. 4 is a View of a tube as shown in Figures 1, 2 or 3, in which in the event of the tube conveying anode current, a series of small luminous lines 9 may be seen, produced by the luminous parts of the wires of the anode.

What is claimed is:

An electron discharge tube for the optical indication of an electrical magnitude adapted to operate at voltages lower than volts comprising a cathode having a given axis, a control electrode, a rellector electrode 1ocated on one side of the cathode, and an anode comprising an elliptical grid located wholly on the other side References Cited in the le of this patent UNITED STATES PATENTS Thompson Mar. 19, 1935 Anderson May 27, 1941 

